Re: [PATCH vfio 11/11] vfio/virtio: Introduce a vfio driver over virtio devices

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On Fri, Sep 22, 2023 at 12:15:34PM -0300, Jason Gunthorpe wrote:
> On Fri, Sep 22, 2023 at 11:13:18AM -0400, Michael S. Tsirkin wrote:
> > On Fri, Sep 22, 2023 at 12:25:06PM +0000, Parav Pandit wrote:
> > > 
> > > > From: Jason Gunthorpe <jgg@xxxxxxxxxx>
> > > > Sent: Friday, September 22, 2023 5:53 PM
> > > 
> > > 
> > > > > And what's more, using MMIO BAR0 then it can work for legacy.
> > > > 
> > > > Oh? How? Our team didn't think so.
> > > 
> > > It does not. It was already discussed.
> > > The device reset in legacy is not synchronous.
> > > The drivers do not wait for reset to complete; it was written for the sw backend.
> > > Hence MMIO BAR0 is not the best option in real implementations.
> > 
> > Or maybe they made it synchronous in hardware, that's all.
> > After all same is true for the IO BAR0 e.g. for the PF: IO writes
> > are posted anyway.
> 
> IO writes are not posted in PCI.

Aha, I was confused. Thanks for the correction. I guess you just buffer
subsequent transactions while reset is going on and reset quickly enough
for it to be seemless then?

-- 
MST




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